Such analytical devices are applied, for example, in process measurements technology, in environmental technology, automatic analytical devices and in industrial measurements technology. For example, analytical devices can serve for monitoring and optimizing the cleaning effectiveness of a clarification plant, e.g. for monitoring activation basins and the clarification plant outlet. Furthermore, analytical devices can be applied for monitoring drinking water or for quality monitoring of food. Measured and monitored is, for example, the content in the liquid sample of a certain substance, which is also referred to as the analyte. Analytes can be, for example, ions, such as ammonium, phosphate, silicate or nitrate, biological or biochemical compounds, e.g. hormones, or even microorganisms. Other measured variables, which are determined by analytical devices in process measurements technology, especially in the field of monitoring water, include total organic carbon content (TOC) and chemical oxygen demand (COD). Analytical devices can be embodied, for example, as cabinet devices or as buoys.
Frequently in analytical devices, the sample to be analyzed is treated by mixing-in one or more reagents, so that a chemical reaction can occur in the liquid sample. Preferably, the reagents are so selected that the chemical reaction is detectable by means of physical methods, for example, by optical measurements, by means of potentiometric or amperometric sensors or by measuring conductivity. For example, the chemical reaction can bring about a coloring or a color change, which is detectable with optical means. The color intensity is, in this case, a measure for the measured variable to be determined. The measured variable can be ascertained, for example, photometrically, in that electromagnetic radiation, for example, visible light, is radiated from a radiation source into the liquid sample and after transmission through the liquid sample is received by a suitable receiver. The receiver produces a measurement signal dependent on the intensity of the received radiation, from which the measured variable can be derived.
In order to use such analytical methods in an automated fashion, for example, for industrial applications or for monitoring a clarification plant or an outdoor body of water, it is desirable to provide an analytical device, which performs the required analytical method in an automated fashion. The most important requirements for such an analytical device are, besides a sufficient accuracy of measurement, robustness, simple serviceability and the assurance of a sufficient working, and environmental safety.
Automatic analytical devices are known from the state of the art. Thus, for example, DE 102 22 822 A1, DE 102 27 032 A1 and DE 10 2009 029305 A1 disclose online analyzers for analyzing samples. These online analyzers are embodied, in each case, as cabinet devices, which include a control unit, liquid containers for reagents, standard solutions and cleaning liquids, pumps for transporting and dosing, or metering, liquid samples, and the one or more reagents, into a measuring cell, and measuring transducers for optical measurements on the liquid sample contained in the measuring cell and treated with the one or more reagents. The reagents, standard solutions or cleaning liquids are transported from the liquid containers and into the measuring cell. Correspondingly, used liquid is transferred from the measuring cell into a waste container. If the waste container or one or more of the reagent supply containers must be replaced, attention must be paid that the hose connections then are connected back correctly. The hoses and the transport pumps are susceptible to material fatigue and must likewise be subjected to maintenance or replaced from time to time.
Described in DE 10 2009 029 305 A1 is an analytical device for automated determining of a measured variable of a liquid sample. The analytical device has one or more liquid containers for one or more liquids, e.g. reagents, a measuring cell for accommodating a measured liquid produced by mixing the liquid sample with one or more reagents and a measuring transducer for providing one or more measurement signals correlated with the measured variable. The analytical device possesses, moreover, a control unit for control of the analytical device and for determining the measured variable based on the measuring signals provided by the measuring transducer. Additionally, the analytical device includes a processing unit controlled by the control unit. The processing unit includes a supply- and dosing system for supplying and metering the liquid sample and liquids from the liquid storage units into the measuring cell. The analytical device possesses at least one replaceable cassette, into which the liquid containers and/or at least parts of the processing unit are integrated.
An advantage of this embodiment is that the liquid containers or wear parts of the processing unit, e.g. hoses, flexible tubing or wear parts of the supply- and dosing system, which must be replaced from time to time by the operating personnel, can be arranged in the cassette. A service person must then, for providing new liquids or for replacing wear parts, only remove the “used” cassette having the liquid containers, or wear parts, and put in a new cassette.
The cassette described in DE 10 2009 029 305 A1 provides, in an embodiment, a housing surrounding the liquid containers, wherein there are integrated in a wall of the housing, for closing the cassette liquid tightly in the state separated from the remaining parts of the analytical device, closeable connectors, which, for example, interact with complementary connectors of liquid lines arranged outside the cassette for forming fluid couplings, in order to connect the liquid containers integrated in the cassette with the external liquid lines. In this embodiment, a number of liquid containers can, without additional effort, be connected, for example, to a processing module arranged outside the cassette. The fluid couplings between the cassette and the outwardly lying liquid lines comprise thus a primary side arranged in or on the cassette and a secondary side interacting therewith and arranged outside the cassette, e.g. in an adapter mounted outside of the cassette. Disadvantageous in such a fluid coupling is that assuring the proper arrangement of the primary and secondary sides of the different fluid couplings relative to one another for implementing the fluid tight connections requires, in the case of connecting the cassette to the analytical device, very complex guiding means for assuring precise orientation of the primary sides relative to the secondary sides. Additionally, there is the danger that the connectors arranged in the outer wall of the cassette can be damaged during transport of the cassette.